The Humen Bridge in Dongguan, Guangdong Province Photo: IC

Authorities in Guangzhou, South China's Guangdong Province, are carrying out a thorough check into a local sea bridge due to apparent abnormal shaking of the bridge over two days. While many netizens are horrified by the shaking, experts explained the phenomenon to ease the public concerns, saying that it would not affect the security and durability of the bridge. 

The Humen Bridge in Guangzhou, China's first large suspension bridge, started to show abnormal shaking on Tuesday afternoon, which made many netizens worry whether the bridge would collapse.

Ge Yaojun, president of the International Association for Bridge and Structural Engineering, told the media on Wednesday that the shaking was probably a result of vortex vibration caused by wind. 

As local authorities are changing the bridge's slings, they put many 1.2-meter-high plastic crash barriers on both sides of the bridge. These barriers changed the bridge's aerodynamic structure and led to vortex vibration when the wind reached a certain speed, according to Ge, who is also engaged in the investigation of the incident.

Local authorities removed the crash barriers on Tuesday but the bridge continued to show small shakes on Wednesday. Ge said that the shakes on Wednesday are not necessarily linked to those on Tuesday and a thorough investigation is underway. 

An engineer from the Humen Bridge management company named Zhang Xinmin told the media that the small shakes are out of inertia and would gradually disappear as the barriers are removed and the wind weakens. 

Suspension bridges are very susceptible to wind, a Beijing-based bridge expert told the Global Times on Wednesday on the condition of anonymity. 

Vibrations caused by wind would happen if the suspension bridge is longer than one kilometer and aerodynamic structure changes in a certain range are acceptable. These factors would not affect the bridge's safety and durability, the expert said. 

In an announcement on Wednesday morning, Guangdong authorities also said that the vibrations would not affect the security and durability of the bridge. 

The authorities imposed traffic controls near the bridge at around 3 pm on Tuesday. The Chinese Ministry of Transport also sent experts to Guangzhou to investigate, according to the announcement. 

The Humen Bridge is nearly 16 kilometers long and was put into use in 1999. It connects Guangzhou and Dongguan, a manufacturing hub in Guangdong. 

According to the expert, the subject of wind engineering for bridges arose in the 1940s after the collapse of the Tacoma Narrows Bridge in the US. When China built the Humen Bridge in the 1990s, the country had fully learned from foreign countries' experiences in the subject.

China has built a complete management system for bridges, but it is the first time for the Humen Bridge to change slings since being put into use and the workers may not have considered such a situation would happen, the expert said. 

Data from this incident will be collected and will help workers to deal with similar situations in the future, he noted.